Method of making compound bimetallic elements



Aug. 2, 1938. s. R. HooD. ET AL 2,125,858 METHOD OF MAKING COMPOUNDBIMETALLIC ELEMENTS Original iied Jan. '2, 1936 '2 Sheets-Sheet 1 I U II IIQVENTOR Y 1 I Y Jf'dfi/eyfiflood BY C/are/rce 5/7/50 ATTORNEY.

' component respectively.

Patented Aug. 2, 1938 1 PATENT -OFFICE METHOD OF MAKING COMPOUND BIME-TALLIO ELEMENTS Stanley R. Hood and Clarence F. Alban, Detroit,

Mich

Original application January 2, 1936, Serial No. 57,220. Divided andthis application June 5,

1936, Serial No. 83,726

'1 Claims. (c1. 29-148) This invention relates to a method of makingbimetallic elements and is a division of our application for LettersPatent of the United States,

Serial No. 57,220, filed January 2, 1936.

The object o1 the invention is to provide a method'for forming acompound bimetallic element of two blades, .the thermal deflections ofwhich are in opposite directions. The action of such compoundbladesdifiers fundamentally from that of the usual single blade in thatit functions due to difference in temperature of its components insteadof the total temperature change.

The uses of such compound blades are to compensate for ambienttemperature changes and to correct errors in calibration due to thermallag.

It has heretofore been common to form a compound blade by riveting orwelding two separate and distinct blades together at one end. Thisinvention distinguishes from such former construction in that by themethod of manufacture, a compound blade is provided that is of a uniformwidth and thickness throughout its length avoiding the unsightly doublethickness and rivet at the weld of the former construction. In one ofthe methods of construction hereinafter described, the dead{ section ofsuch previously lapped, riveted or welded compound blades is avoided.

' It is therefore the purpose and object of this invention to not onlysimplify but to provide a method of construction that is comparativelysimple and inexpensive and resulting in a blade of superior appearanceand greater accuracy in comparison with former compound blades.

These and other objects and the several novel features of the inventionare hereinafter more fully described and claimed, and the preferred formof blade and manner of constructing the same is illustrated in the'accompanying drawings in which---- 7' Fig. 1 is a fi'agmentary blocks ofmetal of a high an Fig. 2 is a similar view showing the assembly of apair. of sucli blocks or strips welded together by theiordinary weldingprocess providing a block 1mm .gy vhich the thermostatic blades may beproducedby rolling and then slitting to the desired Fig. 3 is aperspective view of the blocks of Fig. 2 rolled to a desired thinness.

Fig. 4 is a perspective view of a completed blade as cut from the rolledstock along the line 5 shown in Fig. 3.1 Y

Fig. 5 is an edge view showing the thermostatic blade of Fig; 4 underinfluence of temperature and ture of a bimetallic element.

showing the shape of the blade with a correct ratio of active length ofeach blade which, when heated uniformly, will give zero deflection atthe free end.

Fig. 6 is a perspective view of two blocks of metal, one of lowexpansion component and the v other of high expansion component weldedtosion element of the other.

Fig. 8 is a perspective view showing the blocks when rolled to thedesired thinness.

Fig. 9 is an edge view of a completed blade cut from the sheet Fig. 8.

Fig. 10 is an edge view showing the shape assumed by the blade undertemperature to which both components of the block are subjected.

Fig. 11 is a perspective view showing two blocks, one of a highexpansion coeflicient and the other of a low expansion coeflicientwelded together in a mannerproviding another method of manufac- Fig. 12is a perspective view of the form assumed by the blocks when rolled atninety degrees to the welded surface of Fig. 11.

Fig. 13 is a perspective view showing two strips like that of Fig. 12superimposed one upon the other with the high expansionelement of eachwelded to the low expansion element of the other strip. a

Fig. 14shows the compound bimetallic blade formed by cuttingtransversely of the welded strips shown in Fig. 13.

-The function of the single thermostatic bimetallic blade is well known,the blade having a metal of high coefficient of expansion welded to ametal of a low coeflicient of expansion whereby temperature change tendsto deflect the blade and when held at one end to make or break a contactin an electric circuit for instance,- or the movement of the free endmay be utilized in other ways.

With a compound blade such as herein disclosed, the two blades functionto maintain the contact closed through ambient temperature change as themovement of onepart of the blade may compensate forthe movement of theother part and where the blade is used, for instance with a pilot lightplaying upongone of the elements of a compound blade, the two elementsof the blade function to prevent deflection due to the temperaturechange in the surrounding space.

There are manyuses well known in the art in which our improved compoundthermostatic bimetal blade may be utilized and the invention hereindescribed resides in the construction of the blade and the method bywhich the blade may be manufactured.

The usual bimetallic blade has one side of a metal of low coeflicient ofexpansion to which is secured, as by welding or otherwise, an element ofa high coefiicient of expansion and so far as this invention isconcerned, the compositions of the respective blades are not material asthey may be varied considerably for difierent purposes which are wellknown to persons skilled in the art. Thus, so far as this invention isconcerned, the one element is termed the "low expansion side and theother element the high expansion side".

In the manufacture of our improved bimetallic blade, we form a block orstrip of a metal having a. low expansion coe'flicient indicated at I inFig. 1 which we preferably form with the groove 2 in one side edge. Wealso provide a similar strip or block of metal having a high expansioncomponent indicated at 26w which has a tongue 4 at one edge for engagingin the groove 2 of the low expansion element I. The grain of the metalin both strips or blocks is in the direction of the arrows shown in Fig.1.

The blocks or strips are preferably of the same width and two stripssuch as shown in Fig. 1 may be superimposed one upon .the other inthemanner indicated in Fig. 2 and the meeting surfaces of. these strips arewelded by applying pressure thereto while at welding temperature in theusual manner of making standard bimetal blades. With this arrangement,the low expansion side I of one pair of the strips is welded to the highexpansion member 3 of the other pair and the high expansion side lot thefirst pair is welded to the low expansion side I of the second pair. Theblocks or strips thus welded together in the manner shown in Fig. 2 arethen submitted to the rolling operation and by repeated passes throughthe rolls, the strips are reduced to the desired thinness suggested inFig. 3, the tongue and groove portions being elongated as may be seen inedge view in Fig. .3. This sheet, when rolled to the desired thinness,may be out along the lines 5 to form blades of the desired width asindicated in Fig. 4.

The compound blade shown has equal length 'selection of the alloys usedhaving the necessary physical properties, a compound bimetallic bladehaving peculiar characteristics can be made.

As an example, a blade having certain peculiar characteristics may beproduced by using invar for the element I of Fig. 2 and 42 per centnickeliron alloy for the element I of Fig. 2 and 60 per cent nickel-ironalloy for the high expansion side 3 and 22 per cent nickel 3 per centchrome-iron alloy for the other high expansion side 3 and by correctlyvarying the lengths of the two sections of the blade, an element can beproduced which will have practically no deflection below 350 degreesFahrenheit but will begin to deflect above this temperature. Othercompositions may be used, such for instance as a chromium-nickel ironstrip mounted in reverse relation with an invarpure nickel strip. Such.compound blade may be used for electrical devices, the components beingof diiferent electrical resistivities. Such blade will not deflect atroom temperature variations but will deflect with overload currents.

The blade so far described has a dead section at 'l in Fig. 5 and theratio of the length of the parts of the blade to produce zeromovement isI for the part at the right of the dead section while the part at theleft thereof must be more than 2.4 times the length of the other part.An increase in length of the dead section increases the ratio of thelonger portion to the shorter portion and vice versa. What we havetermed the dead section is the point from which the active length of thelonger blade begins thereby requiring a longer active length to returnor hold the free end to zero position, it being assumed in the abovediscussion that the blade is supported at the short end as indicated at20 in Fig. 5.

To make a compound blade without a dead section between the two partsthereof, we provide a block III of a composition having a low expansioncoeflicient and a block II of a composition having a high expansioncoeflicient which may be welded together at the meeting surface IZ. Theblock has been so welded that it may be out along the lines I3 toprovide aseries of blocks of the desired thickness and .these blocks maybe superimposed one upon the other as indicated in Fig. 7 with the lowexpansion side of one block I0 oppo site the high expansion element IIof the other block. These are then welded together at the meetingsurfaces and rolled to form a sheet shown in perspective in Fig. 8 andin edge view in Fig. 9. Such compound blade will not have a dead sectionand, to provide a blade having zero movement, the ratio should be 1' forthe short side to 2.4 for the long side approximately as indicated inFig. 10. In making the blade from rolled stock it is cut across thegrain along the lines I4.

The method of formation of the improved compound bimetallic blade isapproximately the same in both instances illustrated-that is, a block ofthe low expansion side and of the high expansion side are placed in edgeto edge contact and in reverse relation to a similar pair of strips orblocks. These are welded together at the meeting surfaces, rolled to thedesired thinness and severed across the grain to provide the compoundbimetallic element of the desired width and before or' after rolling oneside of the compound block or rolled sheet may'be cut to the requiredlength in respect to the length of the other side to secure a blade thatwill have zero deflection under temperature change to which both partsof the blade are subjected and by varying the length of one in respectto that of the other, deflection may be produced at any desired point.This, as before stated, can be accomplished through a choice of thecomponents of the respective high and low sides of the two bimetalelements forming the blade.

There is another and possibly superior method ofmaking a compoundbimetallic blade which is indicated in Figs. 11 to 14 inclusive. In thismethod two rectangular blocks 2| and 22 each being respectively of thedesired components and having a thickness preferably about one-half thewidth of the finished blade are welded together along their greatestsurfaces by any approved welding method. This produces ablocksubstantially square in cross section as shown in Fig. 11. Thisblock or bar of Fig. 11 is then rolled at ninety degrees to the weldedsurface to a convenient thickness as shown in Fig. 12 and cut to thestrips beingwelded to the low expansion side ture change.

22 of the other. strip. These two superimposed strips are then rolledlongitudinally as indicated by the arrow in Fig. 13 to the desiredfinished thickness of the bimetallic blade and finallyis out across thegrain to form compound bimetallic blades indicated in Fig. 14. Thismethod is less expensive and is preferable as the material is a 1 littlemore readily handled in the usual rolling operations.

The foregoing description is largely confined to bimetallic devices inwhich there is a constant difference in expansion coeflicient undertempera- It is pointed out, however, that to obtain certain deflectioncharacteristics for some special application or installation, it ispossible to use combinations of metals which have the same temperaturecoeflicient of expansion in one temperature range and differentexpansion rate in another. It is further to be understood that, withinthe scope of this invention, it is also possible to provide a finishedcompound blade consisting partly of bimetal and partly of a singlemetal, as spring material. Therefore the terms high expansion and "lowexpansion as herein used are to be considered only as convenientdescriptive terms. In prac-- tice it is further possible to provide acompound blade by either of the methods herein. disclosed in which thesuperimposed sections have the same expansion coefficient, either in alltemperature .ranges or in a limited temperature range only and as suchlatter character of bimetallic blades are well known to those skilled inthe art, compositions productive of such structures are not specificallygiven.

' It is believed evident from the foregoing description that, by eitherof the methods of manufacture described, a compound bimetallic elementis provided that is of uniform thickness throughout itslength having theappearance of a single bimetallic element and avoiding the ungainlyappearance of the prior' compound bimetallic blades having the weldedand riveted ends and lessening the cost of construction of the same andsecuring a blade that is of greater accuracy in its operation thanpreviously known compound bimetallic blades.

Having thus fully described our invention, its utility and mode ofoperation, what we claim and desire to secure by Letters Patent of ,theUnited States is-- 1. The method of manufacture of a compound bimetallicthermostat which consists in providing two blocks, one having a lowexpansion coeflicient and-the other a high expansion coemeient, forminga tongue in the edge 'of' one of the blocks'to seat in a groove in theedge of the other to form a compound block, uniting two such compoundblocks in a superimposed relationship with the elements of low expansioncoefiicient of each component block opposed to the element of high expansion coefficient of 'the other, and rolling the element of bimetalthermostat which consists in providing a bimetallic blade of rectangularform having a high expansion component secured to a low expansionelement of the same form, welding such block in edge relationship withanother block having its high expansion component on the same side ofthe assembled blocks asthe low expansion component of the first block,the two elements of the second block respectively differing in expansioncoefficients from the elements of the first block, rolling the assembledblocks to provide a sheet of the thickness required in the thermostat,and finally cutting the sheet into stripsto provide the desired width ofa thermostatic blade.

3. The method of manufacture of a compound bimetallicthermostatconsisting in providing two bimetallic blocks of rectangular form andthesame thickness,. welding the same together in edge to edgerelationship with the high expansion component of one of the blocks onthe same side of the assembled pair of blocks as the low expansionelement of the other block, rolling the said blocks to provide a sheetof the desired thinness, and cutting the block transversely of thewelded edge into strips to provide a blade of the desired width andlength and having zero deflection when uniformly heated.

4. The "method of-forming a compound bimetallic thermostat whichconsists in welding a block of a composition having a high coefficientof expansion to a block of like form having a low coefiicient ofexpansion, cutting the welded pair of blocks into a series of blocks ofequal thickness, welding one of the cut blocks face to face, withanother with the elements of low coeflicient of expansion of each cutand welded block respectively opposed to the elements of high coefflcient of expansion of the other block, hot ro lling the pairs ofblocks to provide-a sheet of the desired thickness, and severing thesheet to provide a blade of the desired width.

5. The method of forming a compound bimetallic thermostat which consistsin welding a block of a composition having a high coefficient ofexpansion to a block of like form having a low ooefllcient of expansion,cutting the welded pair.

, to form'a sheet having'a long and a short side,

and severing the sheet transversely of the weld line to provide abimetallic thermostat of the desired width. p V

6. The method of forming a compound bimetallic blade which consists inwelding together two blocks of the desired form in cross section andlength, one having a high expansion coeflicient and the otherhaving alow expansion coefficient, then rolling the blocks at an angle of ninetydegrees to the welded surface thereof to produce a .comparativly thinand long strip with the'material of the low coeflicient of expansion onone side and the material of the high coefficient of expansion on theother, then welding two such strips together with the high expansionelement of .each rip welded to the low expansion pective other strip,and then rolling the w ld'ed trips to secure a blade of the desiredfinished thickness, and finally cutting tively thin and long strip, thenwelding two such strips together with the high expansion element of eachstrip opposite the low expansion element of the respective other strip,then rolling the welded strips longitudinally to secure a blade of thedesired finished thickness, and finally cutting the rolled striptransversely to provide compound bimetallic blades of the desired width.

STANLEY R. HOOD. CLARENCE F. ALBAN.

